A doctoral student in the School of Architecture and Design at the University of Kansas (KU) has developed a low-tech yet adaptively adjustable daylighting solution that combines the benefits of automated controlled daylighting systems and the simplicity of static ones to enhance the distribution of natural light in an interior space.
From static to dynamic
The effectiveness of traditional, fixed lightshelves is limited because they only perform optimally at the time of day when the angle of the earth to the sun is just right. Previous experiments have shown that movable lightshelves and those with curved surfaces can diffuse sunlight with greater efficiency.
So Afnan Barri, a doctoral student of Jae Chang, associate professor of architecture, invented what she named the “Dynamic Thermal-Adaptive Curved Lightshelf (DTACL) — a system that enhances the delivery of natural light into buildings throughout the day, without the use of mechanical and electrical controls... and unlike existing movable systems. Barri reports that between the performance benefit of automated controlled daylighting systems and the simplicity of static daylighting solutions, this adaptively adjustable daylight solution was designed to enhance the distribution of natural light in an interior space.
“The DTACL system is a passive daylight redirecting system,” Barri says. “Unlike traditional passive daylight systems available in the market that are static, this device is movable.” The DTCAL system is capable of actively moving to a curved plane surface. “The influence of a curved plane on distributing daylight deep in a building's interior space can lead to the application of more diffuse sunlight and therefore more of a chance to engage in the overall manipulation of natural light in a building. This would allow for more efficient natural-light distribution in an interior space of a building than traditional horizontal plane lightshelf devices.”
The field experiment and computer simulations
As part of her project, Barri created computer simulations and a field experiment on the KU campus to collect one year worth of data on the performance of the DTACL system in different weather conditions throughout the seasons.
She built four experimental “rooms” outfitted with sensors and lightshelves — one with the DTACL system, two with different types of curved, fixed lightshelf devices, and one static, horizontal plane lightshelf. Barri’s hypothesis: The DTACL system transfers light into a building more efficiently than her fixed systems. And, based on her two-month pilot study and computer simulations, the initial results have proven her right: The DTCAL system enabled an indoor light intensity twice as great as that brought on by a fixed, traditional lightshelf. In most cases, the DTCAL system had the highest light level performance and the traditional fixed horizontal plane lightshelf system had the least amount of light intensity level.
How the dynamic shape change is possible
The DTACL is designed to operate dynamically, without mechanical and electrical control mechanism. The shelf physically reacts to changes in ambient solar and thermal loading conditions. This functionality of DTACL is made possible by an adaptive, composite material called Thermadapt, invented by Ronald M Barrett, a professor of aerospace engineering at the University of Kansas. “The material was constructed and integrated into the lightshelf system and used to create desired curvature movement of the lightshelf for daylighting control,” Barri says.
Adapting to seasons and weather conditions
“The main function of the DTACL system is that during warm seasons, when the sun is at its highest angle and outdoor weather conditions is hot, the material would curve upwards to the highest curvature angle; and during colder seasons, when the sun is at its lowest angle and weather conditions is cold, the material would curve upwards at a lower curvature angle,” the doctoral student illustrates, adding that in a condition where the material is not exposed to solar load or ambient heat, it would maintain a horizontal shaped plane.
DTACL integrates with multiple daylight delivery methods
What’s unique about this innovation and had not been achieved before, is that the Dynamic Thermally-Adaptive Curved Lightshelf is a daylight system that can be integrated in a combination of several different daylight delivery methods used as a set to assist in increasing daylight availability in an interior space of a building and, thus, decreasing artificial light use. Barri says the development of these thermally-adaptive lightshelf mechanisms, which allow for a low-tech yet adaptively adjustable system, merge some of the advantages of active daylighting systems with passive ones. “The hybrid of the two categories was the main influence for the adaptive lightshelf device that will allow for flexible adjustment to daily and seasonal variation of the sun’s path, while retaining a level of simplicity toward low-cost installation and operations.”
What is next?
The next step of this research is to implement and test the performance of the DTCAL device in hot arid climate regions. This experimental study was conducted by the Center of Design Research at the University of Kansas in the northern hemisphere at 38.9° latitude. Barri says she now wants to test the performance of the DTCAL system under different sun latitude angles. The native of Saudi Arabia wants to take the system overseas for experiments in much more extreme temperatures.
Written by Sandra Henderson, Research Editor, Solar Novus Today